An [NU5 onward] consensus rule requiring the `nConsensusBranchId` field to match the consensus branch ID used for SIGHASH transaction hashes, should apply only when effectiveVersion ≥ 5 (since v4 transactions did not explicitly encode the `nConsensusBranchId` field.
An [NU5 onward] consensus rule requiring the `nConsensusBranchId` field to match
the consensus branch ID used for SIGHASH transaction hashes, should apply only
when effectiveVersion ≥ 5 (since v4 transactions did not explicitly encode the
`nConsensusBranchId` field.

Signed-off-by: Daira Hopwood <cd7d43d5556a38ce626d53826fddc46adc597539@jacaranda.org>

zcash/zips,zcash/zips,zcash/zips,zcash/zips